1. Technical Field
This disclosure generally relates to selectively separating carbon compounds containing at least two carbon atoms from a mixed gas stream provided by a chemical process.
2. Description of the Related Art
The modern petrochemical industry makes extensive use of cracking and fractionation technology to produce and separate various desirable compounds from crude oil. Cracking and fractionation operations are energy intensive and generate considerable quantities of greenhouse gases. The gradual depletion of worldwide petroleum reserves and the commensurate increase in petroleum prices places extraordinary pressure on refiners to minimize losses and improve efficiency when producing products from existing feedstocks, and also to seek viable alternative feedstocks capable of providing affordable hydrocarbon intermediates and liquid fuels to downstream consumers.
Methane provides an attractive alternative feedstock for the production of hydrocarbon intermediates and liquid fuels due to its widespread availability and relatively low cost when compared to crude oil. Worldwide methane reserves are estimated in the hundreds of years at current consumption rates and new production stimulation technologies promise to make formerly unattractive methane deposits commercially viable.
Used in the production of polyethylene plastics, polyvinyl chloride, ethylene oxide, ethylene chloride, ethylbenzene, alpha-olefins, linear alcohols, vinyl acetate, and fuel blendstocks such as but not limited to aromatics, alkanes, alkenes, ethylene is one of the most important commodity chemical intermediates currently produced. With economic growth in developed and developing portions of the world, demand for ethylene and ethylene based derivatives continues to increase. Currently, ethylene production is limited to high volume production as a commodity chemical in a relatively large steam cracker or other petrochemical complex setting due to the high cost of the crude oil feedstock and the large number of hydrocarbon byproducts generated in the crude oil cracking process. Producing ethylene from far more abundant and significantly less expensive natural gas provides an attractive alternative to ethylene derived from crude oil. Oligomerization processes can be used to further convert ethylene into longer chain hydrocarbons such as C6 and C8 hydrocarbons useful for polymer gasoline and high value specialty chemicals.
The conversion of methane to longer chain hydrocarbons, particularly alkenes such as ethylene, produces a product gas containing multiple byproducts, unreacted feedstock gases, and inert components in addition to ethylene. The ability to selectively and economically produce and separate methane based alkenes on a commercially viable scale provides a pathway to a significant new source of ethylene useful for production of ethylene based derivatives.